Electrosurgical HF generators are used for treating biological tissue, particularly for cutting or coagulating biological tissue. For this purpose, a generator circuit is provided for generating an HF current, which flows between an active electrode and at least one neutral electrode, via a first current path through the tissue. Accordingly, the generator circuit comprises an active output and a neutral output.
In HF surgery, a distinction is made between the known monopolar and bipolar uses. In monopolar use, the active electrode is configured as an insulated hand-piece, which, for example, has an electrode tip guided by a surgeon to the tissue regions to be treated. An HF current flows through the tissue to a neutral electrode, which contacts the tissue over a large area and is applied, for example, to the thigh of a patient. Such neutral electrodes usually have a contact area of approximately 1 dm2 to 3 dm2. Monopolar applications have the advantage of using a compact hand-piece, the electrode tip of which can also be applied to tissue sites that are difficult to reach. A disadvantage is that the HF current also flows to the neutral electrode through tissue not being treated. Particularly, if the cross-sectional area of the tissue along the current path is small, overheating and damage to regions of the tissue not being treated can occur. This can be counteracted with bipolar instruments. For bipolar instruments, the HF current flows between two closely adjacent electrodes e.g., bipolar coagulation forceps, and therefore exclusively through tissue situated between the clamping surfaces. With these instruments, however, poorly accessible tissue sites can often only be reached and treated with difficulty, or not at all.